package com.kobeliu.entity;
import java.util.Stack;

/**
 * leetCode 2124
 *
 *用两个栈实现一个队列。队列的声明如下，请实现它的两个函数 appendTail 和 deleteHead ，分别完成在队列尾部插入整数和在队列头部删除整数的功能。(若队列中没有元素，deleteHead 操作返回 -1 )

 * 示例 1：
 * 输入：
 * ["CQueue","appendTail","deleteHead","deleteHead"]
 * [[],[3],[],[]]
 * 输出：[null,null,3,-1]
 *
 * 示例 2：
 * 输入：
 * ["CQueue","deleteHead","appendTail","appendTail","deleteHead","deleteHead"]
 * [[],[],[5],[2],[],[]]
 * 输出：[null,-1,null,null,5,2]
 *
 */

public class Demo_28_No2124 {

    Stack<Integer> s1;
    Stack<Integer> s2;

    public Demo_28_No2124() {
        s1 = new Stack<Integer>();
        s2 = new Stack<Integer>();
        }

    public void appendTail(int value) {
        s1.push(value);
    }

    public int deleteHead() {
        if(s2.size()>0){
            return s2.pop();
        }
        if(s1.size()==0) return -1;
        while(s1.size()>0){
            s2.push(s1.pop());
        }
        return s2.pop();

    }
}
